itest: fix testQuiescence

The original test lets Bob send an HTLC to Alice, but Bob doesn't have
any balance to begin with. This commit now fixes it by explicitly
checking sending payment is allowed before quiescence, and forbidden
after.

itest/lnd_quiescence_test.go

@@ -13,9 +13,6 @@ import (
 // testQuiescence tests whether we can come to agreement on quiescence of a
 // channel. We initiate quiescence via RPC and if it succeeds we verify that
 // the expected initiator is the resulting initiator.
-//
-// NOTE FOR REVIEW: this could be improved by blasting the channel with HTLC
-// traffic on both sides to increase the surface area of the change under test.
 func testQuiescence(ht *lntest.HarnessTest) {
 	cfg := node.CfgAnchor
 	chanPoints, nodes := ht.CreateSimpleNetwork(
@@ -26,25 +23,41 @@ func testQuiescence(ht *lntest.HarnessTest) {
 	alice, bob := nodes[0], nodes[1]
 	chanPoint := chanPoints[0]
 
+	// Bob adds an invoice.
+	payAmt := btcutil.Amount(100000)
+	invReq := &lnrpc.Invoice{
+		Value: int64(payAmt),
+	}
+	invoice1 := bob.RPC.AddInvoice(invReq)
+
+	// Before quiescence, Alice should be able to send HTLCs.
+	req := &routerrpc.SendPaymentRequest{
+		PaymentRequest: invoice1.PaymentRequest,
+		FeeLimitMsat:   noFeeLimitMsat,
+	}
+	ht.SendPaymentAssertSettled(alice, req)
+
+	// Alice now requires the channel to be quiescent. Once it's done, she
+	// will not be able to send payments.
 	res := alice.RPC.Quiesce(&devrpc.QuiescenceRequest{
 		ChanId: chanPoint,
 	})
-
 	require.True(ht, res.Initiator)
 
-	req := &routerrpc.SendPaymentRequest{
-		Dest:           alice.PubKey[:],
-		Amt:            100,
-		PaymentHash:    ht.Random32Bytes(),
-		FinalCltvDelta: finalCltvDelta,
+	// Bob adds another invoice.
+	invoice2 := bob.RPC.AddInvoice(invReq)
+
+	// Alice now tries to pay the second invoice.
+	//
+	// This fails with insufficient balance because the bandwidth manager
+	// reports 0 bandwidth if a link is not eligible for forwarding, which
+	// is the case during quiescence.
+	req = &routerrpc.SendPaymentRequest{
+		PaymentRequest: invoice2.PaymentRequest,
 		FeeLimitMsat:   noFeeLimitMsat,
 	}
-
 	ht.SendPaymentAssertFail(
-		bob, req,
-		// This fails with insufficient balance because the bandwidth
-		// manager reports 0 bandwidth if a link is not eligible for
-		// forwarding, which is the case during quiescence.
+		alice, req,
 		lnrpc.PaymentFailureReason_FAILURE_REASON_INSUFFICIENT_BALANCE,
 	)
 }